The photo show a pipe fitting.
The outer pipe is made of copper while is inner is apparently made of 203 steal.
However, the 203 steal become rusted and cannot be opened.
Is there a good way to open it without breaking it?
For instance, perhaps with some chemical etching methods that I can...
In Kraus book on antenna
he mentioned two types of feeding
https://res.cloudinary.com/engineering-com/image/upload/v1488549241/tips/feed_g1ujwf.psd
But what will be the difference for these two methods?
In fluid dynamics there is a duckbill check valve to prevent the reverse flow.
In EM wave an antenna emmits/receive at the same efficiency.
Is there anyway one can make a check valve for antenna so that it emmits more than received or
vice versa.......or perhaps emitts without even receive?
